An image capturing apparatus includes: an image capturing element in which a plurality of pixels are formed and arranged and phase difference pixels are formed within an effective pixel region; a photographing lens; and a control unit which analyzes a captured image signal by the image capturing element, obtains a phase difference amount from detection signals of two of the phase difference pixels that make a pair, and performs a focusing control of the photographing lens, in which the control unit calculates, as a sensitivity ratio, a ratio of an integration value of light receiving sensitivity of the phase difference pixel within a range of an incident angle of the photographing lens, and an integration value of light receiving sensitivity of a pixel other than the phase difference pixel, and corrects a deviation in light receiving sensitivity between the two phase difference pixels.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An image capturing apparatus, comprising: an image capturing element in which a plurality of pixels are formed and arranged in a two-dimensional array pattern and phase difference pixels are formed in a focus detection region within an effective pixel region; a photographing lens which is installed in a stage preceding the image capturing element; and a control unit configured to analyze an image signal captured by the image capturing element, obtain a phase difference amount from detection signals of two of the phase difference pixels that make a pair, performs focusing control of the photographing lens, acquire a first integration value, within a range of an incident angle of the photographing lens, of light receiving sensitivity of a phase difference pixel; acquire a second integration value, within the range of the incident angle, of light receiving sensitivity of a pixel other than the phase difference pixel; calculate, as a sensitivity ratio, a ratio between the first integration value and the second integration value; and corrects a deviation in light receiving sensitivity between the two phase difference pixels that make the pair with the sensitivity ratio to correct the detection signals for acquiring the phase difference amount.
2. The image capturing apparatus of claim 1 , wherein, if the first and second integration values are incapable of being calculated, the control unit is further configured to acquire, at a plurality of points, a ratio of a value of the light receiving sensitivity of the pixel other than the phase difference pixel and a value of the light receiving sensitivity of the phase difference pixel, detected at a predetermined angle within the range of the incident angle; and calculate, as the sensitivity ratio, an average value of the ratio.
3. The image capturing apparatus of claim 1 , wherein the control unit is further configured to calculate a sensitivity ratio by multiplying by each other a characteristic representing a relationship between an incident angle in a pupil-division direction of the two phase difference pixels that make the pair and light receiving sensitivity and a characteristic representing a relationship between an incident angle in a direction, which is at a right angle to the pupil-division direction, and light receiving sensitivity.
4. The image capturing apparatus of claim 3 , wherein when a change of the characteristic, which represents the relationship between the incident angle in the direction, which is at the right angle to the pupil-division direction, and the light receiving sensitivity, is equal to or less than a threshold value and when the range of the incident angle of the incident light is smaller than a threshold value, the multiplication is skipped to calculate the sensitivity ratio.
5. The image capturing apparatus of claim 1 , wherein a sensitivity ratio for each color light is calculated from a distribution of light receiving sensitivity for each of red light, green light, and blue light.
6. The image capturing apparatus of claim 1 , wherein the photographing lens is a lens-replaceable photographing lens, and the sensitivity ratio is acquired after replacing the photographing lens.
7. The image capturing apparatus of claim 1 , wherein the range of the incident angle is a range of an incident angle corresponding to an F number and an image height of the photographing lens.
8. A method for calculating a sensitivity ratio of a phase difference pixel by an image capturing apparatus which includes: an image capturing element in which a plurality of pixels is formed and arranged in a two-dimensional array pattern and phase difference pixels are formed in a focus detection region within an effective pixel region; a photographing lens which is installed in a stage preceding the image capturing element; and a control unit, the method comprising analyzing an image signal captured by the image capturing element; obtaining a phase difference amount from detection signals of two of the phase difference pixels that make a pair; performing a focusing control of the photographing lens, acquiring a first integration value, within a range of an incident angle of the photographing lens, of light receiving sensitivity of a phase difference pixel; acquiring a second integration value, within the range of the incident angle, of light receiving sensitivity of a pixel other than the phase difference pixel; calculating, as a sensitivity ratio, a ratio between the first integration value and the second integration value; and correcting a deviation in light receiving sensitivity between the two phase difference pixels that make the pair with the sensitivity ratio to correct the detection signals for acquiring the phase difference amount.
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March 28, 2014
April 11, 2017
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